PMT module characterization test bench for the MAGIC IACT telescopes

The measurement setup provides short (≈1ns), stable optical pulses at a wavelength of 355 nm with uniform intensity over the module front surface. Optical pulse intensity is variable over a wide dynamic range in increments suitable for accurate photomultiplier linearity measurement. Fixed, repeatable optical pulse intensities are used for single photoelectron spectrum and afterpulsing determination. Operation is automated, requiring around 20 min per module, and is expected to remain stable over the lifetime of the experiment.